Reputation: Sheep are stupid, defenceless and harmless creatures that mope about on hillsides doing not very much. They are good for two things: being eaten and producing wool.

Reality: Sheep are actually surprisingly intelligent, with impressive memory and recognition skills. They build friendships, stick up for one another in fights, and feel sad when their friends are sent to slaughter. They are also one of the most destructive creatures on the planet.

Intelligent. Complex. Sociable. All words we would quickly assign to humans, but would not dream of extending to sheep, those fluffy white creatures you see milling about in fields – or served up with mint sauce on your dinner plate.

Instead, we have decreed that sheep (Ovis aries) are just plain stupid. This opinion has not changed much since the 1700s, when George Washington, one of the Founding Fathers of the United States of America, declared: "If the freedom of speech is taken away then dumb and silent we may be led, like sheep to the slaughter."

Nowadays, to be "a sheep" is to be someone who mindlessly follows others: "a waste of flesh and brain cells," as Urban Dictionary puts it.

A 2001 study by Keith Kendrick, who is now at the University of Electronic Science and Technology in China, found that they can recognise and remember at least 50 individual faces for more than 2 years. That is longer than many humans.

In the study, Kendrick's team trained sheep to distinguish between 25 pairs of sheep, by associating one member of each pair with a food reward.

Sheep also have erotic preferences: 8% are homosexual

"Sheep showed clear behavioural signs of recognising… individuals by vocalising in response to their face pictures," says Kendrick. The team also found evidence that sheep can differentiate facial expressions, and prefer a smile to a frown.

At the time Kendrick told BBC News: "The way the sheep's brain is organised suggests they must have some kind of emotional response to what they see in the world."

Caroline Lee of the CSIRO in Australia has also studied sheep intelligence. She discovered that sheep can learn how to navigate out of a complex maze. The enticing sight of their fellow sheep friends awaiting them at the finish helped them reach the exit.

Aside from being smart, sheep can be playful and joyful. You only need to watch the video of Winter the Jumping Lamb to see for yourself. Sheep also have erotic preferences: 8% are homosexual, making them one of the few species that show lifelong preferences for same-sex partners.

Over two decades ago, researchers from the University of California observed rams for three years and discovered that they established firm friendships and looked out for one another in times of need: "Rams were found to form long term relationships… [they] intervened on behalf of weaker colleagues and supported each other in fights," says the 1993 study.

They were domesticated between 11000 and 9000 BC for the use of their woollen fleece, meat and milk

These acts of loyalty and friendship-building are driven by emotions. A 2009 report published in Animal Welfare found that sheep are capable of experiencing a whole range of feelings, from fear to anger, despair, boredom and happiness.

The researchers gave sheep intermittent access to food from a trough, and then turned on an air blower above the trough at an unexpected moment while they were eating. After the blower came on, the sheep bleated four times more than sheep that were not disturbed, and their heart rates immediately increased.

"[As with humans], despair is triggered by situations which are evaluated as sudden, unfamiliar, unpredictable… and uncontrollable, whereas boredom results from an overly predictable environment," write the authors.

It is ironic how little most of us know about sheep, given how deeply entrenched they are in human culture. They were domesticated between 11000 and 9000 BC for the use of their woollen fleece, meat and milk. The animals have been referred to by different cultures, religious texts and even astrology for thousands of years.

They can deliver a painful kick to anyone who gets too close

For example, the Greek astrological sign Aries is a ram, and in ancient Egyptian religion the ram was the symbol of several gods. Further, the common phrase "to separate the sheep from the goats" comes from a passage in the New Testament. In the story, the sheep (righteous people) find salvation with God, and the goats (sinners) are sent to damnation. Baad goats.

Sheep are thought to have descended from wild mouflon that roamed Europe and Asia. They were particularly common in ancient Mesopotamia, an area that covered a large chunk of what we now call the Middle East, including modern-day Iraq, Kuwait, east Syria and south-east Turkey.

These ancestors had mighty horns with which to defend themselves, but humans have largely bred these out of modern sheep. Nowadays, domestic sheep are bred to be big fluffy creatures, covered in wool that never stops growing so that farmers make money all year round.

However, today's sheep still have a few tricks up their woolly sleeves.

For starters, they can deliver a painful kick to anyone who gets too close, especially if they are defending their young. They can also run fast and scale steep cliffs that many predators are not equipped to handle. Finally, their peripheral vision is impressive: they have horizontal, slit-shaped pupils that allow them to see behind themselves without turning their heads.

The populations of wild animals in Kenya fell by 68% between 1977 and 2016

The world's biggest producer of sheep is China, which is home to nearly 200 million of them. It is followed by Australia at over 70 million, India with over 60 million, Iran with 45 million and Nigeria with 41 million. Sudan has nearly 40 million sheep, while the UK has 33 million and New Zealand nearly 30 million.

In Kenya, where there are estimated to be over 17 million sheep raised for slaughter, the animals are spelling catastrophe for wildlife.

A study published in September 2016 shows that the populations of wild animals in Kenya fell by 68% between 1977 and 2016. The affected species included warthogs, many species of antelope and the rare Grevy's zebra. During the same period, sheep numbers increased by 76.3%.

The effects of drought are much more extreme now

"Aerial monitoring from the government of Kenya shows that sheep numbers have gone up dramatically in the last 40 years," says lead author Joseph Ogutu of the University of Hohenheim in Stuggart, Germany. "Sheep graze grass very low to the ground, and in their huge numbers they decimate the grasslands. This is terrible because most wild animals [like elephants, buffalo and zebra] need taller grasses to eat."

In the Maasai Mara National Reserve, Ogutu says the buffalo population was nearly 13,000 in 1992, but has since sharply decreased. "During the drought, they were pushed out of feeding areas by sheep and other cattle, and the buffalo population crashed by 76% in one year. They've never recovered."

Drought is not uncommon in Kenya, but the issue now is the number of animals, both wild and domesticated, trying to survive it. "The effects of drought are much more extreme now that there are so many sheep competing with wild animals for the same resources," says Ogutu.

Ogutu and his colleagues are calling on the Kenyan government to limit the number of sheep and other livestock, to prevent large wild animals going extinct.

In their huge numbers, sheep are hugely destructive creatures

But what is happening in Kenya is a microcosm for a global story. The demand for livestock products is still rising, putting pressure on the environment.

A 2006 report by the UN Food and Agriculture Organisation explains why: "Extensive grazing occupies and degrades vast areas of land… the livestock sector enters into more and direct competition for scarce land, water and other natural resources… in all, livestock production accounts for 70 percent of all agricultural land and 30 percent of the land surface of the planet."

In their huge numbers, sheep are hugely destructive creatures. Our use of them is contributing to the destruction of forests and to climate change, and causing a shortage of fresh water.

Of course, it is hardly the fault of the sheep. But somehow they do not seem quite so dumb and cuddly any more.